This present invention relates to an apparatus for collecting residual materials dispersed during the imaging of printing plates.
Reference is made to FIG. 1, which schematically illustrates a conventional imaging system, referenced 10, in which a printing plate 12 is externally attached to a drum 14 by means of clamps 16.
The imaging system 10 further includes a laser system 15 comprising an optical system 18 for transmitting a laser beam, referenced 20. The drum 14 rotates as indicated by arrow 22 and the optical system 18 travels axially along the drum""s longitudinal axis. The printing plate 12 may be digitally imaged, that is, information is transferred directly from a computer 11 to the printing plate 12. The laser beam 20, which is controlled by the computerized system 11, effects the exposure of the desired image on the plate.
The printing plate may be an IR sensitive printing member that generally includes an imaging layer comprising an infra-red radiation absorbing material, for absorbing infra red radiation to cause imaging. The imaging layer may consist of an emulsion containing pre-polymer coated onto the surface of the plate. The action of the laser beam hitting the plate causes the material to polymerize. Some unwanted particulate matter is also produced by decomposition in the surface coating and this material is deposited on the plate surface or scattered (indicated by arrows 24) on to the imaging system.
The infra-red radiation absorbing material may include, for example, a carbon loaded organic resinous layer of materials. The carbon may be in the form of graphite, amorphous carbon black, or similar while the organic resins may include binders for the carbon. The material deposited on the plate surface and scattered particles are generally circular of one micron diameter containing carbon.
The deposits of carbon based particles in the interior part of the imaging system can cause severe erosion and wear on the complex moving parts.
In addition, the scattered particles collect on the external face of a glass cover 26 used for protection of the optical system. These particles affect the performance of the laser beam, blocking the rays. In current use, the protective glass cover 26 requires cleaning on a daily basis. The scattered articles are also known to cause artifacts on the imaged plates.
It is an object of the present invention to provide apparatus for collecting residual material, which is scattered and dispersed during the imaging of the printing plate.
There is thus provided, in accordance with a preferred embodiment of the present invention, apparatus and a method for collecting residual material dispersed during the imaging of a printing member attached to a printing drum. The imaging system includes an optical system.
The apparatus provided, in accordance with a preferred embodiment of the present invention, includes a housing circumscribed to the shape of the printing drum, the housing having upper and lower chambers, the lower chamber being configured to be fitted to the optical system, at least one compressed air supply connected to the lower chamber and a suction device which communicates with the upper chamber for extracting the residual material. The air from the compressed air supply is expelled through the lower chamber and drawn into the upper chamber.
Additionally, the method provided, in accordance with a preferred embodiment of the present invention, includes the steps of:
installing a housing onto the optical system proximate to the drum, the housing circumscribed to the shape of the printing drum, the housing having upper and lower chambers;
connecting at least one compressed air supply to the lower chamber;
expelling air at high velocity through the lower chamber;
collecting the dispersed residual material; and
extracting the dispersed residual material via the upper chamber.
Furthermore, in accordance with an embodiment of the invention, the lower chamber includes first and second apertures formed therein through which the compressed air is expelled. The housing is configured so that the expelled air collects the dispersed residual material proximate the housing and the drum.
Furthermore, in accordance with an embodiment of the invention, the first aperture includes an orifice formed within the front face of the lower chamber, the center of the orifice being coincident with the optical axis of the optical system. The lower chamber further includes an annular air cell formed therein, the annular air cell being connected to the compressed air supply. The air cell includes a convergent conic space, the conic space converging towards the orifice.
Furthermore, in accordance with an embodiment of the invention, the second aperture includes a gap formed proximate the bottom face of the lower chamber, the gap being connected to the compressed air supply.
In addition, in accordance with an embodiment of the invention, the bottom face of the lower chamber is configured to have a generally concave shape. The lower chamber further includes a generally circular channel formed therein, the channel being connected to the at least one compressed air supply.
Furthermore, in accordance with an embodiment of the invention, the upper chamber includes a funnel shaped element connected to the upper chamber, the funnel shaped element diverging away from the upper chamber.
The upper chamber further includes a dividing element configured to divide the upper chamber so as to form a second orifice between the dividing element and the top of the lower chamber, proximate to the junction between upper chamber and lower chamber. The dividing element is configured so that the continuation of a central axial line between the dividing element and the top face of the lower chamber through the second orifice intercepts the printing drum at the point of imaging. The dividing element is configured to have a generally concave shape. The shape is similar to the bottom face of the lower chamber.